WO2014184582A1 - Antibacterial micro- and nanoparticles comprising a chlorhexidine salt, method of production and uses thereof - Google Patents
Antibacterial micro- and nanoparticles comprising a chlorhexidine salt, method of production and uses thereof Download PDFInfo
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- WO2014184582A1 WO2014184582A1 PCT/GB2014/051515 GB2014051515W WO2014184582A1 WO 2014184582 A1 WO2014184582 A1 WO 2014184582A1 GB 2014051515 W GB2014051515 W GB 2014051515W WO 2014184582 A1 WO2014184582 A1 WO 2014184582A1
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- A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
- A61L2/16—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using chemical substances
- A61L2/18—Liquid substances or solutions comprising solids or dissolved gases
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- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
- A01N47/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid
- A01N47/40—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid the carbon atom having a double or triple bond to nitrogen, e.g. cyanates, cyanamides
- A01N47/42—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom not being member of a ring and having no bond to a carbon or hydrogen atom, e.g. derivatives of carbonic acid the carbon atom having a double or triple bond to nitrogen, e.g. cyanates, cyanamides containing —N=CX2 groups, e.g. isothiourea
- A01N47/44—Guanidine; Derivatives thereof
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- A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
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- A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
- A01N25/22—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests containing ingredients stabilising the active ingredients
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- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
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- C—CHEMISTRY; METALLURGY
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
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- A61L2420/00—Materials or methods for coatings medical devices
Definitions
- MNPs antimicrobial micro- or nanoparticles
- the present invention relates to an
- antimicrobial micro- or nanoparticle comprising a
- chlorhexidine salt and methods of making and using the same; medical articles and composite materials comprising such antimicrobial MNPs for controlling the delivery of
- Chlorhexidine is a well-known antimicrobial which finds use in various medical applications. These include skin cleansing preparations, hand disinfectants and mouthrinses . CHX is a useful antimicrobial due to its efficacy against both Gram-positive and Gram-negative bacteria and many species of yeast. A further advantage over other antimicrobials is the desirable antibiotic resistance properties associated with CHX. Although individual microbe populations can become less sensitive to CHX when subjected to increasing environmental concentrations, studies have shown that this resistance is temporary and falls when the CHX stimulus is removed.
- CHX The systematic name for CHX is N ! , N ' ' ? ' ' -hexane-1, 6- diylbis [N- ( -chlorophenyl ⁇ ( imidodicarbonimidic diamide ) ] and it has the following chemical formula.
- CHX antimicrobial is an aqueous solution of the readily soluble salt CHX digluconate.
- CHX diacetate CHX diacetate
- CHX digluconate may be delivered to the oral cavity in a mouthrinse, but within minutes the levels of CHX in this aqueous solution are severely depleted. A repeat of the treatment is necessary in order to maintain the delivery of sufficient levels of antimicrobial to the target area .
- a further limitation is that the amount of CHX (e.g. the amount per unit surface area) that can be released from a treated substrate is limited and linked to the concentration of the CHX solution when surface treating with soluble CHX salts in solution, and therefore the antimicrobial efficacy of these solutions is also limited, not easily controllable, and may not be sufficient.
- CHX e.g. the amount per unit surface area
- EP 2462960 A2 discloses a medical indwelling device such as a catheter having an antimicrobial agent.
- the device includes a base material which is a silicone-urethane
- CHX is released from the base material at a rate dependent on the specific copolymer composition. Slow release of CHX is observed over a period of 14 days.
- the applications are limited to coatings on polymeric catheters because the base polymer is required to retain the CHX. Additionally, it would be desirable to provide extended release of CHX to an even greater extent.
- NCHG biocompatible hydrogel
- MPs nanoparticles
- CHX biocompatible hydrogel
- the NPs are polymeric, made from copolymerised 2-hydroxyethy1 methacrylate (HEMA) and
- PEGDMA polyethyleneglycol dimethacrylate
- NCHG cannot be used to confer antimicrobial properties on existing medical articles or compositions.
- the present invention addresses the problems discussed above by providing an antimicrobial micro- or nanoparticle (MNP) comprising a CHX. salt.
- MNP antimicrobial micro- or nanoparticle
- Some of the particular CHX salts proposed herein provide sparingly soluble M Ps which in some aspects display an excellent release profile for CHX over an extended period of months rather than simply days or weeks.
- the CHX MNPs described herein can release CHX gradually for longer than 80 days.
- Other CHX salts proposed herein have a shorter CHX release period but, over a few hours or days, release a very high dose of soluble CHX.
- the release of CHX from samples treated with M Ps of these CHX salts is faster and in larger amount than is achieved from samples treated only with a CHX solution.
- These faster-release aspects may be useful in decontamination applications or to treat particularly stubborn or acute infections or outbreaks.
- the MNPs can find use in a wide variety of applications such as coatings on or embedded within medical articles to confer additional
- antimicrobial properties or as a component of a composite material which can be used to deliver steady doses of
- the MNPs of the present, invention may also exhibit delayed release profiles, or profiles where the release of CHX is triggered by changes in environmental conditions .
- the present invention provides an antimicrobial micro- or nanoparticle comprising a CHX salt
- the present, invention provides antimicrobial micro- or nanoparticles comprising a CHX salt wherein the anio in the salt is selected from oxoanions and partially hydrogenated oxoanions of phosphorus, carbon, nitrogen, and sulphur.
- the anion is selected from oxoanions of phosphorus, carbon, nitrogen, and sulphur, and more preferably the anion is at least one selected from phosphates, carbonate, nitrate or sulphate. More preferably, the anion is selected from phosphates chosen from the homologous series of
- polyphosphates which begins with pyrophosphate and the homologous series of cyclic metaphosphat.es which begins with trimetaphosphate, and oxoanions and partially hydrogenated oxoanions of nitrogen and sulphur.
- the anion is selected from phosphates chosen from the homologous series of polyphosphates which begins with pyrophosphate and the homologous series of cyclic met.aphosphat.es v/hich begins with trimetaphosphate.
- the anion is selected from the homologous series of cyclic metaphosphates which begins with trimetaphosphate, especially hexametaphosphate .
- the MISiPs are nanosized, i.e. the structures have at least one dimension in the range 1 ntn - 1 pm.
- the present invention also provides a colloidal
- the present invention also contemplates methods of making and using antimicrobial MNPs as described herein.
- 'antimicrobial' is meant a substance which acts to kill microorganisms or at least, inhibits their growth.
- the term 'microbe' is used to describe a microscopic organism, such as bacteria, archaea and/or fungi for example. Therefore, antimicrobial compounds and compositions herein may kill these microscopic organisms or at least, inhibit their growth.
- 'phosphates' refers to any phosphorus and oxygen based anion. Phosphates are usually made up of tetrahedrally coordinated orthophosphorus residues.
- Phosphates may be linear, branched or cyclic.
- Exemplary phosphates include phosphates of the homologous series of linear phosphates and polyphosphates which begins with orthophosphate and pyrophosphate, and the homologous series of cyclic metaphosphates which begins with trimetaphosphate .
- Organophosphates are also included within this definition.
- Exemplary organophosphates include alkyl phosphates, such as Ci-e alkyl phosphates .
- micro- or nanoparticle' particles sized between around 1 ran and 100 pm.
- micro- or nanoparticle' is also intended to encompass other suitable micro- a d
- nanostructures such as tubes (both single- and multi- walled), scrolls, rods, cones, "hedgehog” forms, crystals (such as elongate crystals) and amorphous forms.
- Such structures exhibit at least one spatial dimension from around 1 nm to ⁇ , preferably from 1 ran to ⁇ , preferably from 1 nm to less than 1 ⁇ (i.e. "nanostructures” or “nanoscale” dimensions), more preferably from 5 nm to 500 nm, more preferably from 20 to 200 nm, even more preferably from 20 to
- FIG. 1 shows SEM micrographs of borosilicate glass coverslips after immersion in the following compositions .
- FIG 2. shows SEM micrographs of borosilicate glass coverslips after immersion in the following compositions, (e) 5/5 CHX-HMP [10 pm, 6500x] ; (f) 5/5 CHX-nitrate [10 pm,
- FIG. 3 shows CHX elution profiles of orthophosphate, pyrophosphate and triphosphate specimens.
- FIG. 4 shows CHX elution profiles of nitrate
- FIG. 5 shows the following SEM micrographs of alginate wound dressing, (a) control specimen,, no MNPs [60 pm, 2000x] ; (b) CHX-HMP-0.5 MNPs [10 pm, 10400x] ; (c) CHX-HMP-5 MNPs [10 pm, lOOOOx] .
- FIG. 6 shows the following SEM micrographs of
- borosilicate glass covers lips, (a) control specimen, no MNPs [60 pm, 1980x] ; (b) CHX-HMP-0.5 MNPs [10 pm, 9900x] ; (c) CHX- HMP-5 MNPs [10 pm, lOOOOx] .
- FIG. 7 shows the following SEM micrographs of an ethylene vinyl acetate (EVA) polymer some of which incorporate MNPs.
- EVA ethylene vinyl acetate
- FIG. 8 shows the following SEM micrographs on titanium surfaces some of which have been treated with MNPs.
- control specimen no NPs [50 ⁇ , 2080x] ;
- CHX-HMP-0.5 MNPs [10 ⁇ , lOQOQx] ;
- CHX-HMP-5 MNPs [10 ⁇ , ⁇ ] .
- FIG. 9 shows AFM images of the following titanium surfaces some of which have been treated with MNPs (horizontal scale 1 ⁇ , vertical scale 55 nm) .
- FIG. 10 shows AFM images of the following glass surfaces some of which have been treated with MNPs (horizontal scale 1 ⁇ , vertical scale 60 nm) .
- FIG. 11 shows AFM images of the following mica
- FIG. 12 shows the CHX elution profiles from alginate dressings treated with control (25 ⁇ CHX) solution, CHX-HMP- 0.5 and CHX-HMP-5.
- FIG. 13 shows the CHX elution profiles from glass treated with control (25 ⁇ CHX) solution, CHX-HMP-0.5 and CHX-HMP-5.
- FIG. 1 shows the CHX elution profiles from EVA polymer treated with control (25 ⁇ CHX) solution, CHX-HMP-0.5 and CHX-HMP-5.
- FIG. 15 shows the CHX elution profiles from titanium treated with control (25 ⁇ CHX) solution, CHX-HMP-0.5 and CHX-HMP-5.
- FIG. 16 shows cumulative CHX release profiles from glass ionomer cement (GIC) specimens with varying levels of
- FIG. 1/ shows cumulative fluoride release from GIC specimens with varying levels of treatment with CHX-HMP MNPs .
- FIG. 18 shows the following SEM micrographs showing fracture surfaces of GIC specimens, (a) unmodified GIC [20 yaa, 5000x] ; (b) lwt% M Ps [20 , 5050x] ; (c) 2wt% M Ps [20 ⁇ , 5000x] ; (d) 5wt% MNPs [20 ⁇ , 5000x]; (e) 10wt% MNPs [20 ⁇ , 5000x] ; (f ) 20wt% MNPs [20 um, 5050x] .
- FIG. 19 shows Optical Density (OD) measurements at 620nm of CHX and CHX-HMP-5 against MRSA. From these minimum inhibitory concentrations can be calculated. Dark grey bars: 25 ⁇ CHX; light grey bars: CHX-HMP-5.
- FIG. 20 shows Optical Density (OD) measurements at 620nm of CHX and CHX-HMP-5 against P. aeruginosa , From these minimum inhibitory concentrations can be calculated. Dark grey bars: 25 ⁇ CHX; light grey bars: CHX-HMP-5.
- FIG. 21 shows optical Density (OD) measurements at 595 nm following treatment with CHX or CHX-HMP-5 against MRSA. From these biofilm inhibition can be gauged. Dark grey bars: 25 ⁇ CHX; light grey bars: CHX-HMP-5.
- FIG. 22 shows optical density (OD) measurements at 595 nm following treatment with CHX or CHX-HMP-5 against P.
- FIG. 24 shows DLS data showing size distributions of (upper) CHX-HMP-5, and (lower) CHX-HMP-0.5. The three data sets indicate measurements made in triplicate at each
- FIG. 25 shows zeta potential data showing the charge distribution of (upper) CHX-HMP-5, and (lower) CHX-HMP-0.5 Ps .
- the three data sets indicate measurements made in trip1icate for each concentration -
- FIG . 26 shows CHX elution profiles from CMC films (55g CMC per m 2 ) containing particular amounts of CHX-HMP-5 NPs.
- Squares indicate a CMC Mw of 700 kDa and (5 wt% NPs; triangles indicate a CMC Mw of 250 kDa and 6 wt% NPs; crosses indicate a CMC Mw of 700 kDa and 3 wt% MNPs; diamonds indicate a CMC Mw of 250 kDa and 3 wt% NPs; circles indicate a CMC Mw of 250 kDa
- FIG. 27 shows CHX elution profiles from alginate films containing particular amounts of CHX-HMP-5 MNPs. Squares indicate 6 wt% MNPs; diamonds indicate 3 wt% MNPs.
- FIG. 28 shows CHX elution profiles for (diamonds) polyurethane coated with CHX-HMP-5 NPs at 1 dip coat, and (dashes) polyurethane treated with a 25 uM aqueous solution of CHX .
- FIG. 29 shows SEM images showing polyurethane coated with CHX-HMP-5 MPs using (left) 5 repeats [50 pm, 2000x] , and (right) 10 repeats [50 pm, 2020x] of the dip-coating method. Light areas show NP deposition.
- FIG. 30 shows live dead staining images of four microbes grown on polyurethane substrates: (from top to bottom) MRSA; E. coli; P. aeruginosa; and K. pneumonia treated with (from left to right) no MNPs (untreated); CHX-HMP-5 MNPs; and CHX- HMP-50 MNPs.
- FIG. 31 shows CHX release from silicones coated with CHX-HMP-5 NPs with dip coating times of 1 rain (diamonds), 30 mins (squares), 2 hours (triangles) or 6 hours (circles) and a control CHX solution (dashes) for (upper) a body(B) silicone and (lower) a sealant (S) silicone, The medium was refreshed at 8 weeks to account for any saturation.
- FIG. 32 shows CHX release from silicones coated with CHX-TP-5 NPs with dip coating times of 1 rain (diamonds), 30 mins (squares), 2 hours (triangles) or 6 hours (circles) and a control CHX solution (dashes) for (upper) a body (B) silicone and (lower) a sealant (S) silicone. The medium was refreshed at 8 weeks to account for any saturation.
- FIG. 33 shows CHX release from, silicones coated with CHX-TMP-5 NPs with dip coating times of 1 min (diamonds), 30 mins (squares), 2 hours (triangles) or 6 hours (circles) and a control CHX solution (dashes) for (upper) a body (B) silicone and (lower) a sealant (S) silicone. The medium was refreshed at 8 weeks to account for any saturation.
- FIG. 34 shows growth of S. gordon.il on a titanium surface with a coating of CHX-HMP-5 NPs (left-hand, light grey bar) and without, a. coating of CHX-HMP NPs (right-hand, dark grey bar) .
- FIG. 35 shows CHX release from hydroxyapatite discs treated with solutions of aqueous CHX or suspensions of CHX- HMP MNPs of equivalent concentration into deionised water.
- Aqueous CHX data are shown as dashed lines, while MP
- FIG. 36 shows SEM images of the surface of (left) diamond matt emulsion paint [240 pin, 49Ox] and (right) diamond matt emulsion paint [220 ⁇ , 530x] containing 25% by mass CHX-HMP-5 NP paste.
- FIG. 37 shows growth of (left.) MRSA, and (right) E. coli on Diamond Matt paint (negative control, left-hand bars), St.erishie1d paint (positi e contro1 , idd1e bars), and
- Neopaint (paint containing CHX-HMP MMPs, right-hand bars) after 24h incubation.
- the y axis units are in colony forming units (cfu) .
- antimicrobial micro- or nanoparticles comprising a chlorhexidine salt, wherein the anion in the salt is selected from oxoanions and partially hydrogenated oxoanions of phosphorus, carbon, nitrogen, and sulphur.
- the anion is selected from oxoanions of phosphorus, carbon, nitrogen, and sulphur, and more preferably the anion is at least one selected from phosphates, carbonate, nitrate or sulphate.
- MNPs can be formed which are sparingly soluble.
- the MMPs of the present invention can demonstrate a tailored release profile.
- the profile is an extended release profile, releasing a steady level of CHX into a surrounding liquid environment over an extended period.
- the release of CHX is faster and/or in larger amounts as noted above, e.g. in some cases faster and in larger amount than is achievable from a surface treated with a solution of only CHX.
- 'phosphates' includes any phosphorus-based anion composed of tetrahedrally coordinated orthophosphorus residues linked by the sharing of oxygen atoms and derived from the deprotonation of a phosphoric acid.
- phosphate anions which may be used in the present invention are not particularly limited, and may include any anion which comprises phosphorus and oxygen atoms .
- the phosphate anions are monophosphates or polyphosphates.
- the phosphate anions have a linear, branched or cyclic structure,
- the phosphate anions are derived, by removal of one or more hydrogen atoms, from a polyphosphoric acid having the general formula HO(P0 2 OH) n H where n could be any integer but is typically from 1 up to several hundred, preferably 1-10, more preferab1y 1-6.
- the phosphate is selected from at least one of orthophosphate , pyrophosphate, triphosphate or hexametaphosphate .
- Met.aphosphat.es are particularly
- the antimicrobial MNP of the present invention comprises a sparingly soluble CHX salt.
- the MNPs comprise such a salt which has low solubility, the release of CHX from the MNP into the surrounding liquid environment is prolonged.
- the salt is sparingly soluble in this way, the MNPs tend to form a colloidal suspension in water which is advantageous for deposition of the MNPs onto surfaces by dip-coating because it provides a more uniform distribution of the MNPs throughout the liquid and because the charge on the nanoparticles facilitates their adsorption to material surfaces.
- the antimicrobial MNPs of the present invention demonstrate sustained release of soluble CHX in a liquid environment over a long time period. This may be at least 90 days. In other aspects, the antimicrobial MNPs of the present invention demonstrate release of CHX at higher- levels than can be achieved by treatment of surfaces us ng a simple CHX solution. This may be over only a short per od of time (such as periods up to 5 days, up to 1 day, up to 12 hours, up to 6 hours, up to 1 hour, up to 30 mins, up to 10 mins or up to 1 min) , or may be sustained release over longer periods (such as periods up to 90 days, up to 60 days, up to 30 days, or up to 10 days) .
- a short per od of time such as periods up to 5 days, up to 1 day, up to 12 hours, up to 6 hours, up to 1 hour, up to 30 mins, up to 10 mins or up to 1 min
- sustained release over longer periods such as periods up to 90 days, up to 60 days, up
- the chlorhexidine salt is chlorhexidine hexametaphosphate (CHX-HMP) - CHX-HMP is sparingly soluble and so forms a colloidal suspension of MNPs . These MNPs may then be used to coat an article, or may be incorporated into a composite material.
- CHX-HMP chlorhexidine hexametaphosphate
- CHX-HMP is sparingly soluble and so forms a colloidal suspension of MNPs .
- CHX-HMP insolubility of CHX-HMP means that CHX is released slowly and steadily into the surrounding environment.
- CHX-HMP shows an extended release profile for the release of CHX.
- the antimicrobial MMP of the present invention is preferably, the antimicrobial MMP of the present.
- invention shows extended and sustained release in a liquid environment (preferably an aqueous environment) of soluble CHX over a period of at least 7 days, preferably at least 20 days, more preferably at least 30 days, more preferably at least 50 days, more preferably at least 60 days, more preferably at least 100 days, and in some situations at least six months or at least twelve months.
- This extended and sustained release means that CHX is continuously released from the MNPs
- the release rate is about constant throughout this time period although
- embodiments are envisaged in which the release rate alters, e.g. declines, with increasing time.
- This sustained release profile allows the antimicrobial properties of the MNPs to be exploited over a long period of time without the need for ext.ra intervention .
- the antimicrobial MNP consists essentially of a CHX salt, wherein the anion in the salt is selected from at least one of phosphates, carbonate, nitrate or sulphate.
- a CHX salt is present in a particular MNP but that, other components may also be present.
- the CHX. salt makes up at least 40wt%, more preferably at least 60wt%, more preferably at least 90wt% of the antimicrobial MNP, and particularly preferably at least 99wt%. In some situations the CHX salt, may make up 100wt% of the
- the other components in the MNPs may include one or more of polymers (such as polyethylene glycol), fillers, colourants, and agents (e.g. silanes or polylysine) which can facilitate bonding to surfaces or incorporation within composite materials.
- polymers such as polyethylene glycol
- fillers such as polyethylene glycol
- colourants such as silanes or polylysine
- agents e.g. silanes or polylysine
- the higher levels of CHX salt in the MNPs provide enhanced (e.g. stronger and /or longer lasting) antimicrobial efficacy.
- Combinations of the specified anions may also be used to produce the antimicrobial MNPs, for example by co- precipitation of the CHX cation with a mi ture of different anions .
- anions which lead to MNPs which exhibit rapid, release of high levels of CHX may be combined with anions which lead to MNPs exhibiting CHX release at lower levels but over a more prolonged period.
- Such particles may ⁇ be useful, e.g. in medical devices, especially those that are surgically implanted, where the initial high levels of CHX release would counter bacteria present due to the surgery itself and the longer, lower level release of CHX would maintain a clean site over an extended period.
- the antimicrobial MNP comprises a salt of CHX and one anion selected from those listed above.
- the present proposals include a mixture of MNPs comprising CHX
- hexametaphosphate salt with MNPs comprising a CHX salt in which the anion is selected from orthophosphate,
- the antimicrobial MNP in addition to the CHX cation there may be present one or more additional cations in the antimicrobial MNP, for example one or more metal cations, e.g. Cu or Ag.
- the antimicrobial MNPs of the present invention are delayed release particles, i.e. the release of CHX is delayed for a period of time after applying the MNPs to the surface of a substrate or incorporating them into a composite. During this delay period, preferably no CHX is released from the MNPs or, in some cases, the release of CHX from the MNPs during this delay period is at a low rate, e.g. less than 10%, preferably less than 5%, more preferably less than 1% of the eventual release rate immediately following the delay period.
- the MNPs are sensitive to changes in environmental conditions. In such cases, the MNPs may be said to show "smart" properties.
- the release of CHX from the MNPs is triggered by a change in environmental conditions.
- a change in the pH, concentration of a certain trigger component, or temperature of the surrounding environment Even more preferably, the MNP will exhibit a delayed release of CHX, with release of CHX being triggered by a change in the environment such as a drop in pH (i.e. an increase in acidity) .
- a drop in pH may occur upon the formation of a bacterial biofilm so the MNPs release CHX in response to the presence of a bacterial biofilm.
- This may be achieved by, for example, inclusion of a component in the MNPs, or a coating on the MNPs which is responsive to changes in environmental conditions such as those mentioned above.
- the delayed release characteristics may be tailored by selection of an appropriate CHX salt, e.g. by selection of appropriate anion(s), which exhibit a change such as protonation or deprotonation upon the desired change in environmental conditions, e.g. reduction of pH .
- the MNPs show an inherent delayed release of CHX triggered by reduction in pH caused by the presence or formation of a bacterial biofilm.
- the antimicrobial MNPs of the present invention have intrinsic antimicrobial properties.
- the MNPs demonstrate antimicrobial properties in addition to and augmenting the effect associated with release of soluble CHX into the environment. The observed
- antimicrobial efficacy is due not only to the CHX released into solution but is due to the presence of the MNPs
- hexametaphosphate MNPs appear to display inherent
- the antimicrobial MNPs of the present invention may offer antimicrobial properties.
- the antimicrobial MNPs of the present invention may offer antimicrobial properties.
- the antimicrobial MNPs of the present invention may have various structural forms. They may be selected from
- the MNPs are particles or crystals.
- the antimicrobial MNPs of the present invention have a size from 1 nm to 100 pm, preferably from 1 nm to 10pm, preferably from 1 nm to 1 pm (i.e. nanoscale) , more preferably from 5 nm to 500 nm, more preferably from 20 to 200 nm, even more preferably from 20 to 140 nm.
- colloidal suspension comprising an antimicrobial micro- or nanoparticle as described herein.
- the colloidal suspension of the present invention is a colloidal suspension in water.
- Water is a simple and safe solvent to work with and its biocompatibility makes the suspension safe to use in sensitive applications.
- the colloidal suspension of the present invention is a colloidal suspension in an aqueous solution.
- This may be an aqueous solution of CHX.
- the solution may also comprise other dissolved ions or additional components (e.g. surfactant, stabiliser, preservative etc.) .
- the colloidal suspension of the present invention has an absolute value of zeta ⁇ ) potential greater in magnitude than or equal to 15 mV, more preferably greater than or equal to 20 mV, even more preferably greater than or equal to 40 mV and particularly preferably greater than or equal to 50 mV.
- the zeta potential is a measure of the stability of colloidal dispersions and their tendency to form aggregates.
- a high absolute zeta potential value indicates a stable suspension which is less likely to coagulate or flocculate. This is a desirable property making coatings with higher uniformity easier to prepare by dip coating of a substrate .
- the dispersion When the absolute value or modulus of the zeta potential of the colloidal dispersion is at. least 30 mV, the dispersion demonstrates acceptable stability with regards to coagulation. When the absolute value of zeta potential is at least 40 mV the stability of the suspension is excellent, and the
- suspension would not be expected to coagulate and would only show sedimenting behaviour over a long period of time.
- the MNPs exhibit, desirable coating properties and may adhere to the surface of an article to provide a surface coating of antimicrobial MNPs.
- a medical article comprising antimicrobial MNPs as described herein.
- the medical article of the present invention is not particularly limited and may be any article which is intended for contact, with the body, either externally or internally, or for use in a medical environment such as in hospitals or doctors' surgeries.
- Such articles are well-known to those skilled in the art.
- exemplary articles include various types of catheter; oral articles such as dental implants, dentures and mouthguards, wound dressings or medical packaging.
- the medical article of the present invention is a. venous catheter, urinary catheter, dental, implant, mouthguard, dentures, wound dressing or medical packaging.
- Such articles may advantageously be provided with additional antimicrobial properties by functionalisation with the antimicrobial MNPs described herein, e.g. by surface treatment to establish a surface coating comprising the M Ps on the article, or by incorporation of the MNPs into the material of the article itself.
- the medical article of the present invention is a catheter.
- the catheter is be
- antimicrobial MNPs are provided.
- catheters of the present invention which are functionalised with antimicrobial MNPs, colonisation by bacteria is prevented or reduced due to the antimicrobial activity of the MNPs.
- MRSA methicillin-resistant Staphylococcus aureus
- the medical article of the present invention is a dental implant.
- Dental implants are devices used to replace or augment natural bone in the mandible or maxilla (jaw bones).
- An abutment section of the implant protrudes from the gum and prosthetic tooth or teeth are attached to this.
- a problem associated with such implants is their failure in the medium to long term due to colonisation of the implant surface by bacteria and the formation of a pathogenic bacterial biofilm.
- the dental implant comprises antimicrobial MNPs
- the dental implant comprises the
- antimicrobial MNPs in the form of a surface coating.
- the surface of the dental implant is sparsely coated with antimicrobial MNPs.
- area coverage of 25% or less is preferred, preferably 15% or less, more preferably 10% or less, even more preferably 5% or less.
- Titanium is often used to make dental implants because of the useful property of titanium to osseo.integra.te with bone
- a sparse coating of MNPs on the titanium surface is advantageous because the osseointegration can still occur to a significant extent, while still providing the antimicrobial properties associated with the MNPs. If too dense a coating is used then osseointegration is less complete and the junction between implant and bone is weaker. If too sparse a coating is used then the antimicrobial properties of the MNPs are less apparent.
- the medical article may also be a wound dressing.
- a "wound dressing comprising the antimicrobial MNPs of the present invention offers longer lasting antimicrobial efficacy than ordinary wound dressings and other known antimicrobial dressings. This is important in the dressing of wounds including acute and surgical wounds, and chronic or nonhealing wounds .
- the antimicrobial MNPs of the present, invention particularly the CHX hexametaphosphate MNPs, are effective against Pseudomonas aeruginosa bacteria, the most common infectious agent in burn injuries and also against MRSA and Streptococcus gordonii .
- Functionalised wound dressings of the present invention helps to reduce the risk of infection when used to dress wounds including burn wounds and other similar wounds.
- the medical article of the present invention may be a denture product including a denture or palatal obturator.
- a denture product or dentures is a device used in the oral cavity to replace missing teeth and/or sections of palate and restore dental function.
- the underside of dentures which abuts the palate is prone to infection, particularly by the yeast Candida, albicans.
- the MNPs of the present invention particularly the CHX hexametaphosphate MNPs, are effective against a wide variety of yeasts including C. albicans .
- a denture product which comprises the antimicrobial MNPs of the present invention, there is a greatly reduced risk of infection.
- the medical article of the present invention may be a mouthguard. Mouthguards are used in a variety of
- mouthguards are typically made of a polymer such as ethylene vinyl acetate (EVA) and are prone to the formation of EVA.
- EVA ethylene vinyl acetate
- the mouthguards of the present invention comprise the antimicrobial MNPs described herein (either as a surface coating or incorporated into the EVA polymer) which are effective in preventing or slowing the formation of such biofilms, protecting the wearer from infection .
- the medical article of the present invention may be a medical packaging, an operating theatre tray or a medical drape.
- Medical packaging is any kind of packaging used to enclose or protect medical equipment.
- Operating theatre trays are often made of stainless steel and are used to carry sterilised surgical equipment .
- Medical drapes may be any drapes, curtains or other textile used in a medical
- any of these may advantageously comprise antimicrobial MNPs as described herein to reduce or prevent colonisation by bacteria.
- the antimicrobial MNPs may be incorporated into the medical article in various ways, which are not particularly limited .
- the medical article includes a surface coating of antimicrobial MNPs.
- a surface coating can be easily applied by means of dip coating or spray coating.
- the MNPs are incorporated integrally within the article.
- the medical article comprises antimicrobial MNPs embedded within at least an external surface portion of the article.
- the MNPs may be incorporated into the material used to make the article during manufacture, for example during the processing of a polymer for a catheter or the extrusion of the catheter tubing.
- one or more materials that may make up a medical article may be provided with MNPs; for example, they may be dip-coated with M Ps.
- the material comprises: a polymer of medical and consumer relevance such as medical silicones, EVA, and polyurethane , an implant material such as titanium, glass, or a commercial wound dressing.
- the present invention provides a composite material comprising the antimicrobial MNPs as described herein.
- a composite material which comprises these antimicrobial MNPs can release CHX for an extended period as described above in relation to the MNPs themselves. This confers antimicrobial properties on these materials.
- the composite material of the present invention is not particularly limited and may include any material which incorporates the antimicrobial MNPs in order to confer antimicrobial properties on that material.
- Exemplary are materials which incorporates the antimicrobial MNPs in order to confer antimicrobial properties on that material.
- materials include but are not limited to paints, pastes, polymers, hydrogels, and dental cements.
- the composite material of the present invention is a glass ionomer cement, a pai t or an oral care composition. These materials may be advantageously provided with additional antimicrobial properties by including the antimicrobial MNPs within them.
- the following composites containing MNPs have been successfully created: glass ionomer cements, alginate films, carboxymethylcellulose films, paint, and oral care rinse/topical treatment.
- the antimicrobial MNPs are present in the composite material at up to 60wt%, 50wt%, 40wt%, or 30wt%. At levels greater than 60wt% the composite may lose some of its intended functionalitv or structural prooerties due to the large content of MNPs .
- the antimicrobial MNPs are present in the composite material at greater than or equal to lwt%, 5wt%, or 10 t%. At levels below about lwt% the
- antimicrobial properties due to the presence of the MNPs is significantly reduced but may still be adequate for some purposes .
- the composite material of the present invention is a glass ionomer cement (GIC) .
- GICs are used in dentistry for many purposes including as a tooth-coloured filling material, as a luting and lining agent, in Atraumatic Restorative Treatment (ART) , in restorations close to the gingival margin and as a fissure sealant.
- ART Atraumatic Restorative Treatment
- GICs are known to be capable of engaging in ion exchange with the oral
- the composite material comprising the antimicrobial MNPs described herein is a GIC
- CHX leaches out of the GIC and the extended release of CHX from the MNPs may help prevent secondary caries in the area surrounding the GIC treatment.
- the CHX release is sustained for considerably longer than other GICs which incorporate soluble CHX salts such as CHX-diacetate or CHX-digluconate .
- the GICs of the present invention may leach CHX into the
- GICs lack antimicrobial efficacy, and secondary caries (the reoccurrence of tooth decay around or underneath the filling) is a common problem.
- the antimicrobial properties conferred onto the GIC can help to prevent secondary caries.
- the GIC of the present invention is able to absorb CHX from the environment.
- the GIC may be '"'.recharged” with CHX to re-form the original CHX salt MNPs in the GIC when the existing supply is depleted.
- GICs are known to act in this way with respect to the uptake of fluoride from the oral cavity.
- the antimicrobial efficacy of the GIC may continue indefinitely throughout the lifetime of the GIC, replenishing the supply of CHX salt MNPs when .required.
- Use of the antimicrobial MNPs of the present invention means that the intervals between these
- replenishments can be relatively long, e.g. at least 60 or 100 days or even longer, due to the extended release of CHX.
- the antimicrobial MNPs are present in the GIC at from lwt% to 30wt%, more preferably lwt% to 20wt%, most preferably lwt% to 10wt% .
- MNP levels greater than 30wt% the handling properties and tensile strength of the GIC may be detrimentally affected and at levels below about lwt% the antibacterial action due to the presence of the MNPs is reduced .
- the composite material of the present invention may be a paint .
- Antimicrobial paints may be used in operating
- the antimicrobial MNPs of the present invention are efficacious against, a variety of microorganisms including methicillin-resistant Staphylococcus aureus (MRSA) .
- a paint comprising the antimicrobial MNPs of the present invention offers resistance against MRSA among other infectious bacteria.
- microbes which is highly advantageous especially when used in the environments mentioned above.
- the composite material of the present invention may be an oral care composition comprising the antibacterial MNPs as described herein.
- An oral care composition is a material intended for use in the oral cavity for reasons of general hygiene, or treatment of dental caries or a particular periodontal infection.
- the oral care composition is a toothpaste, a protective paste, or a mouthrinse .
- an antimicrobial MNP as described herein comprising reacting an aqueous solution of CHX cations with an anion selected from one or more oxoanions and
- the anion is selected from oxoanions of phosphorus, carbon, nitrogen, and sulphur, and more preferably the anion is at least one selected from phosphates, carbonate, nitrate and sulfate.
- Mixing is preferably in a molar ratio of CHX cations : selected anion of from 1:100 to 100:1 to produce a colloidal suspension of micro- or nanoparticles .
- the two reactants are present at equimolar concentrations, i.e. 50:50.
- equimolar reactant i.e. 50:50.
- the resultant colloidal suspension has satisfactory colloid size and zeta potential.
- concentration of the CHX cation in the reaction mixture is about 5 mM.
- concentration of the anion as described above in the reaction mixture is about 5 mM.
- the method comprises reacting an aqueous solution of CHX cations with a phosphate anion selected from orthophosphate , pyrophosphate, triphosphate and
- the method comprises reacting an aqueous solution of CHX cations with
- HMP hexametaphosphate anions
- the HMP reactant is freshly prepared HMP, e.g. prepared 60 minutes or less before use, to avoid risk of unwanted hydrolysis of the reagent before use.
- one or more additional anions may be present in the reaction mixture.
- one or more additional cations in addition to CHX may also be present in the reaction mixture.
- Additional components may also be present in the reaction mixture. These may be components which are intended to be incorporated into the M Ps, or components which help to prevent agglomeration of the MNPs, e.g. by coating the MNPs after formation.
- PEG polyethylene glycol
- PEG is coated onto the surface of the MNPs after formation.
- the reaction mixture is rapidly stirred throughout the mixing and MNP formation processes.
- the MNPs are retrieved from the colloidal suspension in a further step. This may be achieved by centrifligation at around 21000g for 60 rains followed by removal of the supernatant and drying at 40-60°C for a few days. The resultant particles may then be removed and ground to a fine powder to give MNP aggregates.
- KC1 solution at around 1M concentration may be added to the suspension and left for around 15 mins . This creates charge layer compression, causing the MNPs to sediment. Removal of the supernatant followed by
- centrifLigation at around 5Q00g for 10 mins gives a paste after removal of the supernatant. This may optionally be dried to produce the MNPs .
- a method of forming a surface coating of the antimicrobial MNPs as described herein comprising immersing the article in a colloidal suspension of the MNPs, removing the article from the suspension and optionally rinsing the article with deionised water and drying.
- the suspension is rapidly stirred, e.g. at about 150 rpm.
- the article is immersed in the colloidal suspension for a period of from Is to 30 mins.
- the MNP coverage achieved is related to the immersion time, so if a denser coverage is required the immersion time should be exte ded accordingly.
- the article is rinsed with deionised water after immersion. Rinsing removes excess MNPs from the surface of the article, Preferably, the article is rinsed for a period of from Is to 30s.
- the MNP coverage achieved is related to the rinsing time, so if a denser coverage is required the rinsing time should be reduced accordingly or the rinsing step can be eliminated.
- CHX-HMP MNPs and/or materials functionalised with th CHX-HMP M Ps have efficacy against, a number of microbes, including MRSA, E. coli, P. aeruginosa , K. pneumonia,
- A. baumani i , S. gordonii , P. gingivalis, and C. albicans A number of methods and assays have been used to assess the antimicrobial efficacy, such as total viable counts (colony- forming units), time-kill assays, zones of inhibition, live/dead viability testing, and imaging using a range of microscopy techniques .
- Chlorhexidine based salts were prepared by combining, at room temperature and under rapid stirring, 100 mL chlorhexidine (as the digluconate salt in aqueous solution at a concentration of 10 mM) and 100 mL of one of a range of anions in aqueous solution, also at an initial concentration of 10 mM, to effect final total concentrations of 5 mM of each.
- the anions used are shown in Table 1.
- borosilicate glass coverslips borosilicate glass coverslips .
- Coverslips (Agar Scientific, Stansted, UK) were cleaned by 10 minutes' ultrasonication in acetone followed by 10 minutes' ultrasonication in industrial methylated spirits and allowed to air dry. They were immersed in the 200 mL suspension described above while it was rapidly stirred using a magnetic stirring plate. Coverslips were immersed for 30 seconds, removed, immersed in deionised water for 10 seconds to rinse, blotted to remove excess liquid and allowed to dry in air.
- the resultant glass surface with CHX-based deposits was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) , A benchtop SEM ( Phenom,
- Specimens were coated with a gold-palladium layer using a sputter coater prior to SEM.
- the elution of soluble CHX from the functionalised glass surfaces was examined using ultraviolet spectrophotometry. 8 specimens of each type were placed in individually labelled cuvettes suitable for ultraviolet spectrophotometry. 2.5 mL de ionised water was added to the cuvettes and they were sealed tightly using cuvette lids. These were agitated on an orbital shaker rotating at 150 rpm. The cuvettes were kept sealed and were sampled for chlorhexidine concentration at intervals over a 14 -day period.
- Control sets were prepared where the specimens had been immersed only in deionised water and where they had been immersed only in a 25 ⁇ or 5 mM CHX solution; 25 ⁇ is the concentration of soluble CHX residual in the CHX- HMP suspension and 5 M is the total concentration of (soluble and bound) CHX in the preparations.
- Table 2 shows the CHX release properties of the various CHX salts tested.
- CHX-orthophosphate (CHX-OP) functionalised specimens displayed some areas with a self-assembled porous matrix deposit, but also the unusual structures seen in Figure lb and
- Figure 3a These were composed of arrangements of elongated crystallites which originate from, a central point and extend radially from this point, ("hedgehog" forms). These structures were typically 3Q-50 ⁇ in diameter and the individual.
- crystallites were approximately 0.50-1 ⁇ wide.
- Example 2 CHX-pyrophosphate; Example 3 - CHK-triphosphate;
- CHX-triphosphate (CHX-TP) and CHX-HMP all exhibited similar deposits of a self-assembled porous matrix. This appeared dense and a. more widespread coverage on the CHX-PP and CHX-TP than the CHX-HMP.
- the orthophosphate, pyrophosphate and triphosphate salts of CHX exhibited the hiahest CHX release. These were able to effect a very large release of CHX over a short time, which v/as much greater and faster than the release observed with those specimens exposed simply to a CHX solution.
- the highest release v/as seen from pyrophosphate, an intermediate level from triphosphate and the lowest, from orthophosphate although even this was around 4x the magnitude of CHX release seen from other specimens tested.
- the release in all cases occurred at the initial time with no evidence of sustained release.
- These particles could be used in materials for which a large dose of antimicrobial is required topically.
- An example might be a decontamination treatment for a medical device such as a palatal obturator or denture.
- the hexametaphosphate salts of CHX exhibited the lowest total release of any of the anions, but this was sustained for the duration of the experiment (14 days) and v/as still ongoing at the conclusion of the measurements. In another, longer, experiment the CHX hexametaphosphate salts showed release over at least, a 90 day period. These particles might find
- Example 5 CHX-carbonate; Example 6 - CHX-nitrate
- the nitrate and carbonate salts of CHX exhibited a lower release of CHX than the orthophosphate, pyrophosphate and triphosphate and the release continued over a few days.
- concentration of CHX stabilised and the release can be considered to have come to completion.
- CHX-HMP nanoparticles were prepared by combining, at room temperature and under rapid stirring, CHX (as the digluconate salt in aqueous solution) and HMP (as the sodium salt in aqueous solution) to effect final total concentrations of 5 and 5 or 0.5 and 0.5 raM of each. hese will henceforth be referred to as CHX-HMP-5 and CHX-HMP-0.5.
- 200 rriL of the colloidal suspension was prepared using freshly-prepared reagents (to prevent hydrolysis of the HMP) -
- the specimen was immersed in the rapidly stirred colloid for 30 s, then removed and immersed in deionised water for 10 s to rinse, and then blotted to remove excess liquid and allowed to dry in air.
- nanoparticle-functionalised surfaces were examined using atomic force microscopy (AFM; Nanoscope Ilia, Digital Instruments, CA, USA) for those with suitable surfaces (glass, titanium) but not for those with very rough or uneven surfaces (alginate dressing, EVA polymer) . All specimens were examined using scanning electron microscopy (SEM) (Phenom, Eindhoven, Netherlands) after coating with gold-palladium alloy using a sputter coating unit (SC7620, Emitech, Taiwan) .
- AFM atomic force microscopy
- SEM scanning electron microscopy
- Deionised water was added to the cuvettes and they were sealed tightly using cuvette lids. These were agitated on an orbital shaker rotating at 150 rpm. The cuvettes were kept sealed and were sampled for chlorhexidine concentration at intervals over a 60-90 day period. Control sets were prepared where the specimens were immersed in deionised "water and where they were immersed in a 25 ⁇ CHX solution, which is the concentration of aqueous CHX residual in the CHX-HMP-5 colloidal suspension.
- CHX solution which is the concentration of aqueous CHX residual in the CHX-HMP-5 colloidal suspension.
- NPs may be retrieved from the suspension after the reaction has been carried out. This was not done in the case of the present. Examples, however it may be achieved by one of the following options :
- Nanopar icle Particle size [nm] Zeta potential [mV] prgpcirsuion
- nanoparticle aggregates on most surfaces are nanoparticle aggregates on most surfaces.
- Table 5 shows the CHX release periods for the different functionalised materials. For CHX release quantities, see Figures 12-15.
- Example 12 EVA Polymer CHX-HMP-0.5 -20 days
- Example 13 Titanium CHX-HMP-5 >60 days
- Example 8 Glass functionalised with CHX-HMP-0.5
- the release of soluble CHX ceased after approximately 20-25 days, whereas for the CHX-HMP-5 specimens the release was still continuing at the 90 day point.
- the control group treated with 25 ⁇ CHX did not show any CHX release indicating that the soluble CHX was fully removed by the rinsing step and therefore that the CHX release observed with the nanoparticle-functionalised
- Example 9 Alginate wound dressing functionalised with CHX- HMP-5
- Example 10 Alginate wound dressing functionalised with CHX- HMP-0.5
- Example 11 EVA polymer functionalised with CHX-HMP-5
- Example 12 EVA polymer functionalised with CHX-HMP-0.5 Comparative Example 6 - EVA polymer exposed to control 25 ⁇ CHX solu11 on
- nanoparticles showed the same characteristic nanoparticle aggregates as observed on glass and the alginate wound dressing, although the coverage was typically somewhat less dense than that on the other substrates ( Figure 7) .
- the EVA CHX-HMP-0.5 specimens showed a very low and short-lived release of soluble CHX.
- the CHX-HMP-5 specimens however showed a prolonged release of CHX up to at least 80 days
- Example 14 Titanium functionalised with CHX-HMP-0.5
- CHX-HMP-5 nanoparticles might find application in the development, of antimicrobial coatings for dental and orthopaedic implants fabricated from titanium or titanium alloy, and offer the advantage over traditional antimicrobial coatings that the nanoparticles generate a discontinuous coating with plenty of titanium, still, exposed and available for colonisation by osteoblast cells.
- MRSA Methicillin-resistant Staphylococcus aureus
- NCTC13142 was cultured in Mueller-Hinton (MH) media
- Pseudomonas aeruginosa NCIMB 8626 was cultured in nutrient broth (NB) or nutrient agar (MA) . All cultures were incubated at 37°C aerobically throughout the study.
- the minimum inhibitory concentration (MIC) for the control aqueous 25 ⁇ chlorhexidine and the CHX-HMP-5 colloid against planktonic bacteria was determined by serial doubling dilution (0 - 25 ⁇ ) in a total volume of 100 'dL appropriate media in a 9(5 well microtitre plate (according to British Society for Antimicrobial Chemotherapy methodology for determining MIC) . Cultures were incubated for 16 h at 37 °C in aerobic conditions, optical density (OD) readings were measured at 620 nm (A 620 ) using a standard microtitre plate reader (SpectroStar Nano; BMG Labtech) .
- Biofilms were grown in 50 u ' L appropriate media at 37 °C for 48 h, aerobically then the media was removed and discarded. Loosely adherent bacteria were removed by washing the biofilms twice with 100 ⁇ PBS.
- Chlorhexidine or chlorhexidine nanoparticles diluted in PBS were added to the biofilms using a doubling dilution as described above (0 - 25 ⁇ ) .
- the plates were incubated for 2 h at. 37°C; to estimate biomass, unattached cells were gently aspirated and discarded, and adherent cells were washed twice with PBS and stained with crystal violet (0,25% w/v) for 10 min; following a further two washes with PBS, cell -bound crystal violet was re-solubilized with 7% acetic acid, and absorbance measured at 595 rati (A 595 ) .
- Pre-cultures of MRSA and P. aeruginosa were grown initially for 16 h in appropriate media at 37"C, aerobically. Assays for growth on polymer pieces was determined by placing each cube into the well of a 24 -well TP and adding lml of appropriate liquid media (enough to cover the polymer
- Polymer specimens were EVA polymer as specified in Table 3 which had been cleaned by 10 min ultrasonication in IMS followed by either no treatment (control), 30 s immersion in stirred CHX-HMP-5 followed by 10 s in deionised water (low NP) and 30 s immersion in stirred CHX-HMP-5 without a rinse (high NP). Each well was inoculated with 10 ⁇ of either the MRSA or P. aeruginosa pre-cultures and then incubated for 24 h at 37°C. Polymer specimens were removed from the wells using sterile forceps and transferred to microcentrifuge tubes containing lml PBS. The tubes were vortexes for 1 min to remove adherent bacteria, and cell suspension was serially diluted (10 _1 - 10 "6 ) and bacteria were enumerated using the Miles Misra method.
- Table 6 shows the MIC for control and CHX-HMP-5 media.
- Table 7 shows the effects of different media on static bacterial biofilms of MRSA. and P. aeruginosa .
- Table 8 shows the antimicrobial effects of
- EVA P. a. High levels of bacteria, low turbidity liquid medium
- the MIC for MRSA for CHX-HMP-5 colloidal suspension was found to be an 8x dilution of the colloid, which corresponds to a total (soluble and bound) CHX concentration of 0.625 mM and a soluble CHX concentration of 3,12 ⁇ .
- the MIC for MRSA could not be established for 25 ⁇ chlorhexidine indicating that this solution was not efficacious against MRSA (Figure 19).
- the MIC for CHX-HMP-5 was found to be a 16x dilution of the colloid, which was the minimum
- Biofilms of MRSA were disrupted by the CHX-HMP-5 colloid and to a lesser extent by the aqueous 25 ⁇ chlorhexidine ( Figure 21).
- the CHX-HMP-5 colloid also disrupted biofilms of
- nanofunctionalised EVA polymer for the control polymer P.
- aeruginosa bacterial cells recovered from the specimens were too numerous to count at all of the dilutions used; MRSA was recovered at 5x10 ⁇ cfu ml "'1 .
- MRSA was recovered at 5x10 ⁇ cfu ml "'1 .
- the surrounding liquid media was less turbid than the control (indicating less growth) despite high numbers of bacteria being recovered and that for MRSA the surrounding media was clear, indicating no growth.
- the polymer pieces coated with a high concentration of nanoparticles no bacteria were recoverable for either MRSA or P. aeruginosa and the surrounding media was clear in both instances.
- Aqueous stock solutions of chlorhexidine digluconate and sodium hexametaphosphate were mixed in deionised water such that the final concentration was 4 mM CHX and 5 mM.
- the resulting colloidal suspension was mixed thoroughly and then centrifuged at. 21000g for 60 min. he supernatant was removed and discarded and the NP pellet dried for at least 48 h at 40 °C. The pellet was then removed from the centrifuge tubes and ground to a fine white powder using a mortar and pestle. This powder was added to the GIC by substitution for the glass powder.
- Kemdent, Purton, UK was used as the starting material.
- Cylindrical GIC specimens with nominal dimensions of 6 mm diameter and 3 mm height were formed by mixing the GIC according to the manufacturers' instructions and packing into Perspex molds coated with a thin layer of petroleum jelly to aid removal. The mixing was carried out by individuals with extensive experience of GIC preparation. The precise
- each specimen was immersed in 1 mL artificial saliva in individually labelled vials at 37°C.
- the artificial saliva was composed of CaCl 2 -2H 2 0 0.103gL “! , MgCl 2 0.019gL “x , KH 2 P0 4 0.544glf 1 , C 8 H I8 N 2 0 4 S (HEPES buffer acidic form) 4.77gL _1 , KC1 2.24gL ""1 , 1.80mL 1M HC1, KOH titrated to obtain a pH of 6.8.
- Specimens were periodically removed and placed in duplicate tubes containing fresh artificial saliva such that the artificial saliva the specimen had been incubated in could be sampled for chlorhexidine and fluoride concentrations.
- ⁇ pilot study was conducted to establish the saturation limit of fluoride concentration within the vessels to ensure that the sampling periods were selected appropriately and erroneous readings owing to saturation of the eluent by a fluoride salt were not obtained by leaving too large a gap between readings .
- the sampling occurred at hourly intervals during the first day, followed by intervals of 4 hours, then daily and then weekly. Controls containing only artificial saliva without a GIC specimen were sampled in the same way.
- Chlorhexidine concentration in the artificial saliva was measured using ultraviolet (UV) spectrophotometry.
- UV ultraviolet
- the 1 mL artificial saliva was placed into a semi-micro cuvette
- Fluoride concentration in the artificial saliva was measured using an ion selective electrode by mixing 0.5 mL artificial saliva with 0.5 mL TISAB solution. The data output was converted to mg/ ' L fluoride ion with reference to
- Indirect tensile strength was measured by applying a compressive diametric force to the cylindrical specimen until fracture occurred, recording the load at fracture and using this to calculate tensile strength.
- Example 21 Good >33 >33 15.5 (1.1) days days
- Table 10 shows cumulative CHX release. Within each timepoint, letters indicate statistically homogeneous groups, so figures with different letters are statistically
- Table 11 shows cumulative fluoride release. Within each timepoint, letters indicate statistically homogeneous groups, so figures with different letters are statistically significantly different, to a 95% confidence level at that time .
- CHX release over 791 h (33 days) normalised to surface area can be seen in Figure 16.
- a dose-response was evident, in that specimens with a higher substitution of CHX-NPs exhibited a larger CHX release, although the relationship was not directly proportional.
- Fluoride release over 791 h (33 days) normalised to surface area can be seen in Figure 17. All of the GIC specimens released fluoride continually over the duration of the experiment. The initial release rate was the most rapid and this gradually slowed over the experimental period.
- Diametral tensile strength of the 6 specimen groups are shown in Table 3.
- the ANOVA gave a p value of 0.054
- nanoparticle substitution exhibited a slightly different, appearance ( Figure 18f) , with evidence of more smaller particles or nanoparticle aggregates.
- CHX-HMP nanoparticles By adding CHX-HMP nanoparticles to a commercial GIC, it has proven possible to create a material which releases CHX for an extended period in a dose dependent manner. Since CHX is efficacious against a wide range of bacteria and yeasts, this confers antimicrobial and anti-caries properties on these novel nanofunctionalised dental filling materials.
- nanoparticles and nanoparticle aggregates were indicating the presence of nanoparticles and nanoparticle aggregates. These higher substitutions could lead to a reduction in strength since they cannot be presumed to interact with the polyacid in the same way as the glass filler- particles.
- the nanofunctionalised GICs showed the same fluoride release profile as the unmodified cements.
- CHX-HMP nanoparticles described herein as opposed to other approaches such as using ground up CHX diacetate or an aqueous solution of CHX digluconate, offers the advantage that the CHX release is sustained for
- EVA specimens were functionalised by 30 s immersion in a colloidal suspension of CHX-HMP-5 in water followed by 10 s immersion in deionised water ("low concentration”) or without subsequent immersion in deionised water ("high concentration).
- CHX attributable to the released CHX. This may be due to a localised much higher concentration of CHX which is highest close to the surface of the material; and/or the nanoparticles having inherent antimicrobial activity.
- Example 26 Microbiology on titanium samples functionalised with CHX nanoparticles
- Titanium specimens functionalised with CHX-HMP-5 were also exposed to cultures of Streptococcus gordonii bacteria.
- the samples were immersed in 2 mL growth medium and incubated for a maximum of 8h, According to the release experiments this should result in a release of around 7 ⁇ per m 2 .
- the surface area of specimen was 0.00024 m" so the expected release should be 1.7 riM CHX into 2 mL giving a resultant
- Streptococcus bacteria to S. gordonii also implicated in dental caries has been reported as 0.125% CHX digluconate by mass which corresponds to around 1.4 mM, i.e. four orders of magnitude higher than the CHX concentration effected by the present specimens .
- CHX-HMP-5 and CHX-HMP-0.5 NPs were deposited on carbon-coated copper grids (Agar Scientific Ltd., Essex, UK) and subjected to TEM and EDX (Jeol 120 kV 1200 Mk2 ; Jeol, Tokyo, Japan) .
- TEM grids were immersed in NP suspensions for 2 s, rinsed in deionised water for 2 s and allowed to dry in air.
- FIG.23 shows an example of a CHX-HMP-0.5 sample on the left and a CHX-HMP-5 sample on the right.
- the image of the higher concentration sample shows that MNPs can be seen at the periphery of an aggregate (top right of the image) , with good visibility of individual nanoparticles .
- Two examples of separate, individual nanoparticles are indicated by arrows.
- TEM suggests that, the MNPs are often fused together, and not just held electrostatically (see especially the image for the lower concentration sample) . Some very small aggregates were also observed.
- EDX was carried out CHX-HMP MNPs on TEM grids to investigate the composition of the MNPs Both CI (from CHX) and P (from HMP) were observed in the spectra, confirming that the MNPs are composed of CHX and HMP. Signals from Cu and Au are attributed to the TEM grid on which the MNPs were deposited.
- 3Q particle sizes measured using DLS were different for CHX-HMP-5 and CHX-HMP-0.5, giving average values of 202 and 140 nm, respectively.
- the values obtained by DLS were slightly larger than that revealed by TEM (TEM analysis suggested values of approximately 40-80 nm) , which is thought to be a result of
- dry alginate Protanal LF 10/60 FT, FMC Biopolymers
- CMC carboxymethyl cellulose
- CMC was found to dissolve rapidly on immersion in water, disintegrating and releasing all of the CHX over a period of approximately 10 minutes. CHX release reached completion within minutes and was dose dependent, with the higher wt% MMP-containing films showing a longer time to complete release (FIG. 26) .
- the alginate MNP films of example 28 have been tested in antimicrobial assays.
- the test microorganisms are considered to be very relevant to wound infection: MRSA, Escherichia coll, Pseudomonas aeruginosa / Klebsiella pneumoniae and
- Acenltobacter haumanii is the first rriicrobe reported to have a resistance against CHX by means of an ion transport, channel in the cell membrane . It is not a widespread pathogen but is found particularly in hospitals of the armed forces.
- Table 12 shows zones of inhibition for experimental CHX-HMP MNP alginate composite dressings for 5 wound-associated pathogens compared with a commercial silver-based dressing, and indicate that for MRSA, E. coli f P. aeruginosa and K.
- the MN dressings inhibit bacterial, growth to a greater extent than the commercial dressing.
- the silver dressing has a larger zone of inhibition than the MNP dressings for A. haumanii , but it is considered
- Example 32 Surface-coated materials: polyurethane catheters Polyurethane substrates and catheters have been coated with CHX-HMP-5 MNPs.
- Coating density has been investigated by changing the reagent concentration (50 mM of CHX and HMP) and the dip-coating regime (1, 5 and 10 dip repeats) . It has been found that longer dip-times result in more release, and that 50 mM MP concentration in most cases releases more than a 5 mM
- the polyurethane specimens coated with CHX-HMP-50 exhibited no growth of MRSA, E. coll and P. aeruginosa and a reduction in growth of K. pneumoniae (examples 33-36) compared to controls treated with water (comparative examples 15-18) or an aqueous CHX solution (comparative examples 19-22).
- FIG. 30 The lighter areas of FIG. 30 indicate areas of microbe growth. So, high levels of microbe growth are seen in the untreated control (comparative examples 23-26, leftmost column of FIG. 30). These images show the effect of the MNPs on microbial growth (middle and right columns of FIG. 30) and indicate that microbial growth is radically reduced by the presence of the MNPs at either concentration (examples 37-44). Mote that the MNPs themselves take up some of the fluorescent dye, which can be seen as bright areas in the CHX-HMP-50 images (examples 1- 44) .
- Silicones are used as prostheses and other biomaterial devices throughout the body.
- the particular focus of this example is silicones used in the oral cavity, in the construction of palatal obturators (devices used to correct defects in the palate owing to surgery or developmental anomalies) and dentures .
- the CHX release from three formulations has been investigated following dip-coating oral silicones for a range of times from 1 minute to 6 hours.
- Body (B) and sealant (S) represent two different kinds of silicone as supplied.
- the elution medium was refreshed at 8 weeks to account for any saturation.
- specimens of a 'body' and 'sealant' silicone used during denture soft lining and obturator construction (Mucopren Soft; Kettenbach, Eschenburg, Germany) , were created using silicone molds measuring 5 x 8 x 2.5 mm.
- the molds were greased using petroleum jelly, the silicone was packed into the molds and allowed to cure at room temperature for 15 minutes.
- the specimens were then removed from the molds and ultrasonicated in 70% ethanol for 10 minutes, dried in air for 15 minutes and stored dry in sealed containers.
- CHX release from three formulations was investigated following dip-coating of oral silicones for a range of times from 1 minute to 6 hours.
- CHX-HMP MNP coated specimens exhibited a gradual release of CHX over the experimental period.
- the rate of release decreased with time, but when the artificial saliva was replaced the rate was increased again, suggesting that the degree of saturation of the artificial saliva with respect to the CHX salt was hindering release of CHX before the
- CHX-TP MNP coated specimens exhibited quite a different CHX release profile from CHX-HMP MNP, with most or all of the CHX release observed in the first 24h period. A small additional CHX release was observed following artificial saliva change, but again this small release reached completion within the first 2 h after the artificial saliva was introduced.
- CHX-TMP MNP coated specimens like those coated with CHX-TP MNP, exhibited most or all of their CHX release within the first. 24h of exposure to artificial saliva, both at the outset and after the artificial saliva was refreshed. Coating time effected CHX release but in a different manner from the other salts: the greatest CHX release was observed for those specimens coated for
- CHX-HMP MNPs have been used to coat titanium to develop antimicrobial coatings for implants.
- CHX-HMP-5 MNP-coated titanium, substrates prepared by immersion in CHX-HMP-5 suspension for 30 s, rinsed in
- CHX in aqueous solution is in already in use in dentistry. It. is available in. supermarkets and pharmacies as a 2.2 mM oral rinse suitable for controlling plaque and periodontal
- Three aqueous solutions of CHX digluconate were prepared, 1, 2.2 and 5 mM (comparative examples 34-36, respectively)
- Three CHX-HMP MNP suspensions were prepared with matched total concentrations, so with 1, 2.2, 5 mM of CHX and HMP (examples 52-54, respectively) .
- Hydroxyapatite discs were immersed in the preparation for 15 s, rinsed, and the CHX release observed as a function of time (FIG. 35) .
- Example 55 and Comparative Example 37 - Antimicrobial paints Methods of sequestering the MNPs as a suitable paste for use in antimicrobial paints have been carried out and prototypes have been created with 25% by mass MNP paste in an emulsion paint, and compared with a market leading antimicrobial paint (Dulux Sterishield) .
- the NP paste was created by preparing 400 mL CHX-HMP-5 by mixi g 200 mL 10 mM CHX digluconate with 200 mL 10 mM sodium HMP at room temperature and pressure during vigorous mixing. Approximately 50 mL 1M KCl was added, and then the stirring was ceased. The resulting mixture was allowed to sediment and the top ⁇ 3Q0 mL clear supernatant discarded. The remaining liquid was centrifuged for 20 minute at 5000 rpm in a benchtop centrifuge, which resulted in separation of supernatant and a viscous white paste with a consistency between paint and toothpaste. The supernatant was again discarded and the paste removed from the tubes and used.
- the experimental paint was viable (example 55, FIG. 36, right image), drying apparently normally (by eye) and with a similar surface finish to the unmodified paint (comparative example 37, FIG. 36 left image) .
- MRSA and E. coli were investigated on the negative control (unmodified emulsion, comparative examples 38-39), experimental (NP doped) and positive control ( Sterishield, comparative examples 40-41) paints after 24h incubation in the bacterial cultures. Glass cove.rsl.ips were coated on both sides with a single coat of the paints and allowed to dry.
- Sterishield effected a 10-fold reduction in growth of MRSA, but the MNP paint effected a 1000-fold reduction in the same (FIG, 37).
Abstract
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JP2016513444A JP6506258B2 (en) | 2013-05-17 | 2014-05-16 | Antimicrobial microparticles and nanoparticles comprising chlorhexidine salts, method for their preparation and use |
ES14725531T ES2732599T3 (en) | 2013-05-17 | 2014-05-16 | Antibacterial microparticles and nanoparticles comprising a chlorhexidine salt, production method and uses thereof |
DK14725531.9T DK2996468T3 (en) | 2013-05-17 | 2014-05-16 | Antibacterial micro- and nanoparticles comprising a chlorhexidine salt, process for the preparation and uses thereof |
US14/891,951 US9717248B2 (en) | 2013-05-17 | 2014-05-16 | Antibacterial micro- and nanoparticles comprising a chlorhexidine salt, method of production and uses thereof |
CN201480028812.5A CN105228447B (en) | 2013-05-17 | 2014-05-16 | Including the antibacterial micron of chlorhexidine salt and nano particle and its preparation method and application |
CA2947930A CA2947930C (en) | 2013-05-17 | 2014-05-16 | Antibacterial micro- and nanoparticles comprising a chlorhexidine salt, method of production and uses thereof |
BR112015028752-2A BR112015028752A2 (en) | 2013-05-17 | 2014-05-16 | antimicrobial micro- or nanoparticles comprising a chlorhexidine salt, method of production and uses thereof |
EP14725531.9A EP2996468B1 (en) | 2013-05-17 | 2014-05-16 | Antibacterial micro- and nanoparticles comprising a chlorhexidine salt, method of production and uses thereof |
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US10640463B2 (en) | 2016-03-18 | 2020-05-05 | Queen Mary University Of London | Chlorhexidine crystal forms and uses thereof in medicine |
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US20190117569A1 (en) * | 2017-10-24 | 2019-04-25 | Saint Anthony Biomedical, LLC | Compositions and methods for reducing infection in wounds and surgical sites |
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US20070212419A1 (en) * | 2006-02-18 | 2007-09-13 | Jozsef Bako | Synthesis of biocompatible nanocomposite hydrogels as a local drug delivery system |
WO2011009083A1 (en) * | 2009-07-17 | 2011-01-20 | Carefusion 2200, Inc. | Particles incorporating antimicrobial agents |
WO2012119155A1 (en) * | 2011-03-03 | 2012-09-07 | American Dental Association Foundation | Antimicrobial compositions for tooth fluoridation and remineralization |
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JPS59227824A (en) * | 1983-06-10 | 1984-12-21 | Unitika Ltd | Antibacterial latex composition |
US7820734B2 (en) * | 1998-10-07 | 2010-10-26 | Tyco Healthcare Group Lp | Antimicrobial lubricious coating |
FR2792532B1 (en) | 1999-04-26 | 2001-12-21 | Menarini France Lab | NOVEL ANTISEPTIC COMPOSITIONS AND THEIR PROCESS FOR OBTAINING |
JP2003089606A (en) * | 2001-07-12 | 2003-03-28 | Kanae Toryo Kk | Hinokitiol sustained release agent |
WO2008089822A2 (en) * | 2007-01-23 | 2008-07-31 | Merck Patent Gmbh | Antimicrobial composition comprising zinc oxide, barium sulphate and silver ions |
BRPI0802906A2 (en) | 2008-06-27 | 2011-03-22 | Comunidade Evangelica Luterana Sao Paulo Celsp Universidade Luterana Do Brasil Ulbra | nonionic dentifrice and its production process |
US20110293690A1 (en) * | 2010-05-27 | 2011-12-01 | Tyco Healthcare Group Lp | Biodegradable Polymer Encapsulated Microsphere Particulate Film and Method of Making Thereof |
US20120150131A1 (en) | 2010-12-09 | 2012-06-14 | Teleflex Medical Incorporated | Polymer for Controlling Delivery of Bioactive Agents and Method of Use |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US10640463B2 (en) | 2016-03-18 | 2020-05-05 | Queen Mary University Of London | Chlorhexidine crystal forms and uses thereof in medicine |
US11578035B2 (en) | 2016-03-18 | 2023-02-14 | Queen Mary University Of London | Chlorhexidine crystal forms and uses thereof in medicine |
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ES2732599T3 (en) | 2019-11-25 |
GB2516537A (en) | 2015-01-28 |
US20160128332A1 (en) | 2016-05-12 |
CA2947930A1 (en) | 2014-11-20 |
JP6506258B2 (en) | 2019-04-24 |
EP2996468A1 (en) | 2016-03-23 |
GB2516537B (en) | 2015-11-25 |
JP2016521681A (en) | 2016-07-25 |
US9717248B2 (en) | 2017-08-01 |
CN105228447B (en) | 2018-07-20 |
GB201408748D0 (en) | 2014-07-02 |
CA2947930C (en) | 2021-07-13 |
DK2996468T3 (en) | 2019-07-01 |
BR112015028752A2 (en) | 2018-01-23 |
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JP2019073536A (en) | 2019-05-16 |
EP2996468B1 (en) | 2019-04-10 |
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